Discharge tube



Oct. 11, 1932. E. OOSTERHUIS ET AL DISCHARGE TUBE Filed July 11, 1927 llll WVVE/V 70/? S Ek/rq 005 he rh u is Patented Oct. 1932 UNITED STATES PATENT OFFICE .EKKO OOSTERHUIS AND JOHANNES GIJ'SBEBTUS 'WILHELM MULDER, OF EINDHOVEN,

NETHERLANDS, ASSIGNORS TO N. V. PHILIPS GLOEILAMPENFABRIEKEN, OF EIND- HOVEN, NETHERLANDS, A LIMITED-LIABILITY COMPANY r niscrmnen TUBE Application filed July 11, 1927, Serial No. 204,968, and in the Netherlands October 9, 1926.

Discharge tubes of this kind havehitherto been provided with anodes consisting of metal, for example of iron or nickel. It has.

been found that such metal anodes give rise to a very harmful disintegration, probably due to the fact that positive ions produced in the arc discharge between the cathode and one of the anodes, when the full tension is applied in inverse direction between the cathode and the other anode, impinge on this anode. It has therefore hitherto appeared to be impossible to manufacture rectifiers of the type so as to have a sufficient length of life. According to the invention this disadvantage is obviated by the use of carbon anodes and a gaseous filling preferably of one of the rare gases of suitably chosen pressure, such as a pressure of the magnitude of 1 millimetre or more generally a pressure (lying preferably between 0.5 and 5 mm. of mercury). As a rule the discharge tubes will be designed for voltages lying between 80 and 400 volts. As the disintegration mentioned above occurs at the surface of the anodes, the latter may instead of being entirely of carbonconsist of a core of material other than carbon coated with a layer of carbon. The term carbon must be understood to include also graphite.

Care should, in general, 'be taken that the anodes extend in the discharge tube so far that during the operation of the tube positive ions practically cannot impinge on the wires to which the anodes are secured, the disintegration of these wires being consequently prevented thereby. However, the said wires may also be coated with an insulating material, for example with glass, which also prevents the wires from being struck by positive ions, so that disintegration cannot occur.

The invention will be more clearly understood by referring to the accompanying drawing representing a front and a side view of a discharge tube for rectifying both In the figure, .1 is a discharge tube connected in a circuit arrangement which permits to rectify both half-waves of an alternatmg current which enters at A and B.

Being known per se, this circuit arrangement will not be described in detail. Pole wires 3 and 4: for an oxide incandescent cathode 5 and pole wires 6 and 7 for two anodes 8 and 9 are mounted in a stem 2 of the discharge tube. These anodes which, in accordance with the invention, are made of carbon are shaped into a cylinder and are screwed on to the threaded pole wires. The anodes in the discharge tube reach so far and the distance between the incandescent cathode and the metal anode pole wires is, therefore, so great that the latter cannot be struck by positive ions. The discharge tube is filled with argon at a pressure lying between 0.5 and 5 mm. of mercury. The discharge produced during the operation of the tube has the character of an arc discharge.

What we claim is:

1. A gasfilled discharge tube for rectifying both half waves of an alternating current ranging in voltage between 80 and 400 volts, having a filling of argon at a pressure lying between 0.5 and 5 mm. of mercury, a substantially centrally located electronemitting-oxide cathode, and provided with cylindrical anodes consisting at least superficially of carbon and located at each side of the cathode respectively, the active surfaces of which anodes are of relatively great radius of curvature as compared with that of the cathode, and which anodes have ends at a point remote from the emitting surface of the cathode, and conductors for the anodes connected at said remote ends whereby the conductors are substantially protected from being struck by positive ions.

2. A gasfilled discharge tube for rectifying both half waves of an alternating current ranging in voltage between 80 and 400 volts, having a filling of rare gas at a pressure lying between 0.5 and 5 mm, of mercury, a substantially centrally located electronemitting-oxide cathode, and provided with cylindrlcal anodes consisting at least superficially of carbon and located respectively at each side of the plane through the center of the cathode,

the active surfaces of which anodes are of relatively great radius of curvature as compared with that of the cathode, and which anodes have ends at a point remote from the emitting surface of the cathode, and conductors for the anodes connected at said remote ends whereb the conductors are substantially protected fom being struck ositive ions.

y testimony whereof we aflix our signatures, at the city of Eindhoven, this 27th day of June 1927. v

EKKO OOSTERHUIS.

- .lOl lANNES GUSBERTUS WILl-IELH MULDER. 

